1. Field of the Invention.
The present invention relates to electroplating apparatus and methods and more particularly, to methods and apparatus for plating of printed circuit boards and the like.
2. Prior Art.
In U.S. Pat. No. 4,174,261, methods and apparatus for providing high and uniform processing rates for electroplating, deplating, etching and the like, substantially independent of the surface geometries of the article subjected to the process are disclosed. In accordance with that process in an electroplating application, the article to be plated is supported on a cathode so that the electrolyte may be forceably sprayed on the article from an array of spray nozzles adjacent the surface thereof. Intermixed with the array of spray nozzles may be a second array of openings providing suction to locally remove most of the sprayed electrolyte after impingement on the workpiece. The net effect is that fresh electrolyte is constantly being sprayed onto the article being plated, including being sprayed into thru-holes of a printed circuit board, with the spent electrolyte being quickly removed from the workpiece before it has an opportunity to shield the surface thereof from the spray of fresh electrolyte. Functionally, the method and apparatus of that patent work very well, resulting in uniform, very high density plating on flat surfaces, and very good distribution along relatively deep thru-holes in printed circuit boards, not generally achievable with other techniques. The process is less than optimum however from a energy and noise standpoint, as a relatively high pumping power is required to give the best results, and the process itself is relatively noisy, particularly with multiple tanks operating in a typical production environment.